The invention concerns a liquid filter, in particular an oil filter for an internal combustion engine, comprising a hollow-cylindrical filter element that can be flowed through radially from the exterior to the interior by the fluid to be filtered and has on at least one axial end face an end disk, wherein the cleaned fluid can be axially drained from the interior of the filter element, and further comprising a drain plug at an end face of the interior of the filter element wherein the drain plug forms a valve member and is axially adjustable between a closed position and an open position, and, in the open position, a drain passage for draining fluid is open, wherein the drain plug is connected to the filter element or a component that is fixedly connected to the filter element.
EP 1 307 274 B1 discloses a liquid filter for lubricant oil of an internal combustion engine which comprises a hollow-cylindrical filter element disposed in a filter housing and flowed through in radial direction from the exterior to the interior by the oil to be cleaned. Into the cylindrical interior that constitutes the clean side, a support tube is loosely inserted which is connected with a cover of the filter housing so that, upon removal of the cover, the support tube is also removed from the interior of the filter element.
On the side that is opposite the cover, a valve body of a slide valve is attached to the support tube by means of a snap-on connection wherein the valve body is formed as a rod-shaped oil drain plug that can be adjusted between a closed position and an open position. In normal operation, the oil drain plug is in the closed position in which a drain passage for soiled oil is closed off. Upon opening the cover, the support tube is lifted out of the interior of the filter element and the oil drain plug is adjusted into the lifted open position in which the drain passage is opened for drainage of the soiled oil. Upon further lifting of the cover, the snap-on connection relative to the oil drain plug is released so that only the support tube is removed while the oil drain plug, on the other hand, stays within the filter housing.